Nida-Core polypropylene honeycomb

[weavis]

I have to attach some fittings through Nida-Core polypropylene honeycomb. A couple of holes have to go through to the deck.

One of the methods I am considering is using aluminium stiffener plates either side for deck fittings.

My questions for those that know the materials, is what would I uses in the holes to seal the exposed honeycomb, and whether Aluminium is an OK metal to use?

[paxfish]

I would first drill oversize, paint the core with regular epoxy, stir in high density filler like 404, fill hole with thickened epoxy, cure, sand, then drill the proper size hole. Then you don't have to worry about compressing the core or compromising it with water.

After that, backing plates can be many different materials. Consider butyl tape for sealing instead of caulk, depending on what you're doing (what are you doing?)

[weavis]

Originally Posted by paxfish

I would first drill oversize, paint the core with regular epoxy, stir in high density filler like 404, fill hole with thickened epoxy, cure, sand, then drill the proper size hole. Then you don't have to worry about compressing the core or compromising it with water.

After that, backing plates can be many different materials. Consider butyl tape for sealing instead of caulk, depending on what you're doing (what are you doing?)

Right now Im drinking coffee.. what are you doing?

A cleat and possibly a new small winch.

Thanks for the advice.... I have 404 and some resin. I dont have Butyl but its only a store away.

[Zach]

Take a core sample where you need to mount your hardware with a 1/2 inch grit hole saw.

It depends if you are going over something that was a pre-fab type NidaCore panel or if it was built in mold, and whether it is fiberglassed both sides or has a gelcoat only face on the inside. If it is dead flat like a deck on a power boat, then you probably are looking at a panel product... If it is curved, then you need to take a core sample and see what thickness glass you have on both sides. If you've got a balanced layup you can do your backfill from the top. If they've got a single layer of roving on the inside and a layer of veil you'll want to work from the underside.

Nothing sticks to the polypropelene honey comb, so you have to do your best to skin down to the fiberglass under the edges if you choose to back fill it.

With the flat panels most guys end up with 30 ounces or so of cloth, can be roving and mat, or biax... on the top side of an 18 once panel so that the deck is tough enough to live with for winch handles and such. That means your best course of action is to do your backfilling work from the inside... Where most folks leave the single 18 ounce pre-finished surface.

If you have the stuff that is 18 ounce woven roving both sides... I normally take a hole saw and pop a hole in the inner skin just smaller than the backing plate and ream out the core with a top bearing bit on a laminate trimmer. It is easy to jump across a 2-3 inch hole with a few wooden sticks screwed to the laminate trimmer. Then you can either back fill with chopped glass fiber, or if it is a T-Top or console alternate 1708 and mat... or take a piece of Coosa or Penske board and bond it into place if you need a hand rail mount.

If it is one hole, for something like a antenna mount... I normally back fill with chopped glass fiber. If you have a dozen or so that adds a lot of weight and I use Coosa...

The last wild card on flat panel is a Nida Core panel that is fiberglass one side and gel-coat on the unfinished side... It's the cheapest of the "Flat" composite panels that are prefinished. When I see this... it normally takes a backing plate that is three layers of 18 oz biax laid up on glass and bond that to the underside gelcoat surface and then follow up with a metal plate that is narrower than the backing plate if possible. Otherwise you'll just key-hole the honeycomb around the backing plate.

If you are over machinery space and have the room, bonding a fiberglass angle iron to the underside and tapering the edges stiffens up the panel a bit. If you point load Nida-Core panels it starts to sag if you are beside hatches and it wasn't done over framing.

Cheers,

Zach

[Roy M]

For light loads, follow paxfish's suggestion. For the winch, which is in serious sheer, add a pretty large backing plate, in addition, say, double the width of the winch base. That should spread the load over a large enough area of the deck underside to do the trick. And the butyl tape is also a great idea for dynamic loading.

[paxfish]

Originally Posted by weavis

Right now Im drinking coffee.. what are you doing?

A cleat and possibly a new small winch.

Thanks for the advice.... I have 404 and some resin. I dont have Butyl but its only a store away.

I think for either of those, aluminum would be fine, as would a quality plywood backer.

Butyl is nice because it conforms to the surface and doesn't dry out over time...I think I got 10 yards for $10 from ebay...

[a64pilot]

Since it's Honeycomb, would you want a tube insert in the hole to prevent crushing the Honeycomb? Tube being short enough to allow limited compression.

[weavis]

Wow! Thanks for all the advice.

Im away from the boat right now, but I think the cleat is being placed on a flat moulded in area. I can get at the underneath and it looks like GRP.

No idea on placement of the winch...... Have to look next time Im there.

[GordMay]

Originally Posted by a64pilot

Since it's Honeycomb, would you want a tube insert in the hole to prevent crushing the Honeycomb? Tube being short enough to allow limited compression.

➥ http://www.shur-lok.com/product_dls/Design_Manual.pdf

➥ http://www.shur-lok.com/product_dls/..._Structure.pdf

[weavis]

Originally Posted by GordMay

➥ http://www.shur-lok.com/product_dls/Design_Manual.pdf

➥ http://www.shur-lok.com/product_dls/..._Structure.pdf

Thanks Gord.

[mikereed100]

Great advice so far. Another option that I used on our boat under the winches and cleats is to remove the honeycomb from underneath and replace it with high density Corecell. You would then glass over the exposed Corecell with a thick layer of fiberglass that extends well beyond the footprint of the hardware. Let paranoia be your guide here. You would still over-drill the holes and fill with epoxy as with any cored panel. Another vote for butyl rubber.

[canadian cat]

G10 panel is even better than Alu. plate. No corrosion with your stainless fasteners.

McMaster-Carr

[UNCIVILIZED]

- Oversize drill the holes for your fasteners, perhaps a bit more than "normal".
- BOND a G10 or Aluminum plate to the deck's undersided. Fill with epoxy & milled/chopped fibers.
- Bond the "backing" (AKA reinforcing) plate of your choice to the deck. Be it; Aluminum, G10, DIY G10, or Vacuformed wood/glass laminate.

DIY G10 is just layers of cloth (or better, knitted or stitched axials) & epoxy, which you make on your work bench with a cheap vacuum system. Followed by a post cure if you like.
It doesn't necessarily have the full properties of purchased G10, but is easier to work with with tools (it's properties depend on your skills, materials, & setup - but 60k+ psi isn't overly tough to achieve)

The neat part about it though, is, you can put wood layers into the laminate, especially on the outer skins. And due to the vacuum used in making the stuff, the wood gains an enormous amount of strength. As the vacuum will literally pull epoxy all of the way through thin layers (3-6mm+) of wood.
Which, when coupled with glass layers in the laminate, or carbon fiber if you want, then you have some gorgeous backing or deck plates, which are also Seriously strong.
Just protect them from UV, & make sure that they're well sealed.

Carbon Fiber G10 type laminates are stronger than Aluminum when done right. And definitely add cool factor points.

Also, if where you want to mount your backing plates has a funky or unique curvature. You can use mold release, or packing tape on the area in question, prior to laying up the custom backer in situ, with a vacuum setup. And once things have cured, peel off the backer, clean up it's edges & such. As well as de-waxing it & the deck, & then bond it in place.
~ Either that, or;
-> Break out the grinder, & shape them to fit.
-> Bond them in some structurally thickened epoxy. Say, with milled, or chopped fibers.

PS: If you want to mount hardware so that no nuts protrude into the headliner, you can either;
- Get an over-thick piece of G10 for the backer, & machine recesses into it for nuts & washers, in addition to tapping the G10.
- Get an over-thick piece of G10, & drill & tap it for about 85% of it's thickness, so that your bolts don't penetrate it, bevel/bullnose it's edges, & then paint to match your headliner.
- Drill & tap the full thickness of the G10, & after installing the deck hardware, put a thin wooden trim piece on top of it, as well as a bull nosed trim ring around it's edges.


Hope that's not a case of TMI. Just trying to help out the newbies ;-)

NOTE: Use caution on epoxy back fill pours of any size, if they're deep (1cm or more) so that things don't go exothermic on you.